This invention relates to a loom and, more particularly, to a detector for detecting weft yarn inserted into the shed of the loom.
As is well known, air-jet looms are so constructed that a number of groups of weft yarn guide members each having an opening are arranged in alignment together on the slay so that the openings form a weft yarn guide passage, through which each weft yarn passes during one cycle of the weft insertion. In such a loom, one or more of the guide members has a weft yarn detector disposed therein to determine whether or not the weft yarn has passed through the weft yarn guide passage. For example, this type of weft yarn detector is shown in U.S. Pat. No. 4,188,981 and German Laid-Open specification No. 2,105,559.
Typically, each group consists of a predetermined number of weft yarn guide members fixedly mounted in a base to be formed into a single unit, and these separate units are then attached to the slay. Therefore, with respect to the particular guide member having the detector disposed therein as mentioned above, it must be installed into the associated base at the time the other guide members are installed, or after the other guide members have been installed. In the latter case, it is necessary to reserve a space in which the particular guide member is to be installed later on. This means that the detector is allowed to be arranged only in a preliminarily selected, fixed position.
However, as is well known in the art, a loom is required to produce woven cloth having a wide range of widths. Therefore, a detector in a fixed position may not effectively detect the weft yarn, depending upon the range of changes in the width of the cloth.
In order to remove this disadvantage of the position fixed detector, it has been provided to insert and mount a detector between adjacent guide members in a manner allowing the detector to move along the direction of the weft insertion. This provision enables the detector to be always positioned in an optimum detecting position even if the cloth width is changed by a large margin. Such a detector is disclosed in U.S. patent application Ser. No. 100,408 filed by H. Suzuki et al. and assigned to the same assignee as the present application.
At this point, it is to be noted that the spacing between the adjacent guide members is generally the same as, or smaller than, the effective thickness of the detector, because the detector has to be provided with photoelectric or magnetic detecting elements and wiring therefor. Thus, the detector has to be forcedly inserted between the adjacent guide members by spreading out them laterally, so that they are apt to be deformed, especially when they are made of plastic. This deformation will cause irregularities in the weft yarn guide passage, which may adversely effect the insertion of the weft yarn thereinto, resulting in failure of the insertion.
It is therefore a principal object of this invention to provide a weft yarn detector which can be formed so as to have a relatively small thickness and therefore mounted in position without adversely affecting weft yarn guide members on both sides thereof.